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Re: What can make DNS lookups slow?




On Wed, 12 Jan 2005, Daniel L. Miller wrote:

> Chris Evans wrote:
> 
> >running on the machine.  So with /etc/resolv.conf as:
> >cat resolv.conf
> >search psyctc.org
> >nameserver 127.0.0.1

unless the machine is running dns ( named, bind )...
127.0.0.1 should be removed

> >nameserver 213.120.62.97
> >nameserver 213.120.62.98
> >nameserver 213.120.62.99
> >nameserver 213.120.62.100
> >nameserver 213.120.62.101
> >nameserver 213.120.62.102
> >nameserver 213.120.62.103
> >nameserver 213.120.62.104

if one of those is also your gateway, use it ...
	say your gateway is 213.120.62.100
	and remove the rest of um

each of those should be running named or bind, and if not,
remove it
	- you only need 1 or 2 or 3 of um

the list should be the same as the dns servers listed for  psyctc.org
	Name Server:NS0.INTERCITYUK.COM  ( 195.82.119.192 )
	Name Server:NS0.BLACKCATNETWORKS.CO.UK 193.201.200.34
	Name Server:NS1.BLACKCATNETWORKS.CO.UK 69.55.225.40

	- so remove all of yoru dns server at 213.*
	unless it is your local dns server for your machine
	in your lan

- sounds like oyu need to either setup a dns server
  for your internal lan ... ( if you have one )

c ya
alvin
  
> Each computer that requires domain name resolution requires a list of 
> one or more servers (that's your resolv.conf). 

or the dumb way is to use /etc/host files and list what you need 
in the silly file ( which should be removed when there is more than
one machine ... you dont want to update /etc/hosts on each server

> Now, contrary to some 
> people's belief, the resolver does NOT go through a list of servers 
> looking for a valid response.  Instead, it starts at entry #1 and tries 
> for resolution.  As long as that server responds - that counts as a 
> successful resolution.  "No such host" is a valid result - which means 
> that's the end of your workstation trying to resolve www.abc123dontask.com.

yup

> Let's say you have your own DNS server that is authoritative for your 
> LAN - located at 192.168.0.1.  This server has a list of all your local 
> hosts - and that's ALL it knows about!

and it cn also know about how to find a gateway to the other networks 
 
> Now, in your workstation's resolv.conf, you list 192.168.0.1, along with 
> your service provider's primary/secondary servers.

you do NOT need to use your isp server .. if you run your own dns
 
> Now you have a single source of DNS for your LAN - that when queried, 
> can return an answer for both your LAN and the Internet.

that's the right way
and a backup that automatically copies its files from the "master"

  If you 
> need/want a backup - then you need a backup cache, that again points to 
> both a source of internal DNS and to a service provider's DNS.

isp is OUT of the picture and is not required if dns is  
properly setup for your domain

> So now, every workstation, and server - including the firewall, should 
> have the following extensive resolv.conf:
> 
> domain mylocal.domain
> server 192.168.0.1

  # one more, just in case dns dies on 192.168.0.1
  server w.x.y.z 

c ya
alvin



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